Patent GB-1346898-A (GB)
Title: Automatic control systems
IPC: G05D1/02
Filed: 1970-04-29
Abstract: 1346898 Programme control EMI Ltd 4 June 1971 [29 April 1970] 20487/70 Heading B7N [Also in Divison H4] In an automatic control system for vehicles, especially driverless tugs which are steered automatically along a path defined by guide conductors carrying alternating current, the guide conductors are arranged in sections along the path, each vehicle is arranged to transmit a unique identification signal into the guide conductors and central control means coupled to at least some of the sections receive the identification signals so as to identify vehicles at predetermined positions in the system to compare the position of a vehicle with a stored programme relating to that vehicle and, in dependance upon the comparison, to control the progress of the vehicle. General arrangement.-As described, the system is provided with a block control unit at each junction between conductor sections for preventing a vehicle from passing into the next section if there is another vehicle in that section as disclosed, for example, in Specification 1,181,419 and at decision points such as route divergences or convergences and loading or unloading bays, the identification signal of the vehicle must be transmitted from the appropriate block control unit to the central control unit for the vehicle programme to be carried out. The identity signal is in the form of a frequency-shift keyed binary word and is separated from the steering signal (of different frequency) by filtering. It is suggested that the central control may interrogate all sections in turn or alternatively may be arranged to interrogate only occupied sections. In a further arrangement the central control may interrogate only all newly occupied sections. Block control unit. Fig. 2.-The additional circuitry required at decision points is shown as dashed lines. A 2KHz steering signal is generated at 101 and supplied via channel 103 of filter 102 to a conductor section Sn. The received identity signal of around 9KHz from a vehicle in section Sn is supplied via channel 104 of filter 102, amplifier 105, threshold detector 106, inverter 107 and gate 109 to inverter 110, oscillator 101 being disabled when no signal is provided from inverter 110. The output of detector 106 is also supplied via conductor 108 to the central control circuit to indicate that section Sn is occupied. The output of inverter 110 is again inverted at 111 and supplied as an inhibit signal to other sections, similar signals from other sections being used to inhibit gate 109. A decoder 116 enables gates 117, 118, 120 on receipt of the correct section address on conductor 114 from the central control, the identity signal being supplied via gate 120, amplifier 121 and conductor 115 to the central control. At the central control the vehicles identity is correlated with the programme for that section and a "set" or "reset" signal is sent to the block control unit via conductor 112 or 113 respectively. A "set" signal inhibits gate 109 via a bi-stable 119 to stop the vehicle whereas a "reset" signal cancels a "set" signal if present and does not affect the progress of the vehicle.